I know this has been covered before, but I don't see why this wouldn't work.
As with most xdrive owners that have stock suspension, I can fit four fingers in the gap from the top of the tire to the fender. My car currently has 225/45/17s (63.43 centimeter diameter) all around. I want to upgrade the wheels to 19s, but also increase the diameter in order to fill some of the wheel gap without lowering.

This would mean picking a higher profile tire for the new wheels, but still maintaining 1% or less for the rolling diameter. With the setup of 235/45/19 (69.41 centimeter diameter) front and 265/40/19 rear the front wheel gap alone would be reduced by 2.4 inches (6 centimeter increase in diameter over stock). This combination also allows the rolling diameter to be 0.1%

Why wouldn't this work? Am I missing something? That seems like a major decrease in wheel gap without having to drop. I don't think that the 2.4 inch increased diameter in the rear would cause it to rub.

I know this has been covered before, but I don't see why this wouldn't work.
As with most xdrive owners that have stock suspension, I can fit four fingers in the gap from the top of the tire to the fender. My car currently has 225/45/17s (63.43 centimeter diameter) all around. I want to upgrade the wheels to 19s, but also increase the diameter in order to fill some of the wheel gap without lowering.

This would mean picking a higher profile tire for the new wheels, but still maintaining 1% or less for the rolling diameter. With the setup of 235/45/19 (69.41 centimeter diameter) front and 265/40/19 rear the front wheel gap alone would be reduced by 2.4 inches (6 centimeter increase in diameter over stock). This combination also allows the rolling diameter to be 0.1%

Why wouldn't this work? Am I missing something? That seems like a major decrease in wheel gap without having to drop. I don't think that the 2.4 inch increased diameter in the rear would cause it to rub.

Any thoughts?

Right after I typed the post above, I check tirerack.com and they don't carry 265/40/19 tires. DAMN!!!!

Your speedometer and odometer will be off by over 8% and the dealership will - correctly - deny warranty service on suspension and drivetrain bits.

On second thought, the dealer may deny any warranty service because of the odometer issue.

What calculation are you using? Here is an example: Running 235 45 18s up front and 265 40 18s rear there is only 0.1% difference in the speedometer based on the calculated rolling radius. That is almost perfect, although it isn't what BMW would recommend. This setup would also take 1.4 inches from the front wheel gap.

Tires that much larger than stock are not a good idea for numerous reasons. I would also suggest getting the car checked out as a 4 finger gap would be 3 inches by my hand and is twice the gap of my stock car. I realize it is more than the stock RWD by a MASSIVE 1/2 inch but let's not make it seem like a SUV.

In all seriousness do a suspension change if the gap is not to your liking. Not only will it fix the visual but it will make the car more fun to drive.

What calculation are you using? Here is an example: Running 235 45 18s up front and 265 40 18s rear there is only 0.1% difference in the speedometer based on the calculated rolling radius. That is almost perfect, although it isn't what BMW would recommend. This setup would also take 1.4 inches from the front wheel gap.

Simple - go to the wheel and tire forum and plug in your two tire sizes. BTW, in your first post you talked about going to a 265/40/19 tire. That would result in a 8.6% difference from stock.

If the size difference is minimal, then why do you think that wheel gap would be reduced?

Please re-read your original post and plug the numbers into the calculator.

Simple - go to the wheel and tire forum and plug in your two tire sizes. BTW, in your first post you talked about going to a 265/40/19 tire. That would result in a 8.6% difference from stock.

If the size difference is minimal, then why do you think that wheel gap would be reduced?

Please re-read your original post and plug the numbers into the calculator.

I used the calculator to get those numbers. You can only take the difference the 8% difference from stock into account as detrimental if I went 265 45 19 all around, which would be stupid. Instead, like I said in my original post, I was suggesting going 225/45/19 front and 265/40/19 rear. Now the wheels and tires are staggered and would mean the rolling diameter is very similar 0.1% between the four of them Isn't this the same in principle as what other XI owner do when they go staggered and commonly go 235/35/19 front and 275/30/19 rear, which amounts to around 0.2% difference between the four.

I used the calculator to get those numbers. You can only take the difference the 8% difference from stock into account as detrimental if I went 265 45 19 all around, which would be stupid. Instead, like I said in my original post, I was suggesting going 225/45/19 front and 265/40/19 rear. Now the wheels and tires are staggered and would mean the rolling diameter is very similar 0.1% between the four of them Isn't this the same in principle as what other XI owner do when they go staggered and commonly go 235/35/19 front and 275/30/19 rear, which amounts to around 0.2% difference between the four.

Keeping the rolling diameter between the four wheels is one thing, but you want to increase the diameter of all 4 by over two inches. Half of that is going to slightly close your gap while the other half will raise your car. The increased diameter will screw up your speedometer and odometer readings that will cause the dealer to refuse service.

not going to work, you seem to not realize that the more rubber you add to the top to close the gap, the more rubber will be on the bottom between the rim and the road.

you're GAP will not decrease without shorter springs. Your ride height (ground clearance) will also skyrocket and make the car handle like shit.

It would still make the gap smaller between the fender. The hub is a fixed point. Expanding the diameter will decrease the fender gap along with a slighter increase in ride height (smaller due to compression of the tire due to weight.)

Personally I don't think doing what the OP is proposing will do anything bad mechanically and it may just set the speedo at a more accurate speed. Currently they read high as it is.

It would still make the gap smaller between the fender. The hub is a fixed point. Expanding the diameter will decrease the fender gap along with a slighter increase in ride height (smaller due to compression of the tire due to weight.)

Personally I don't think doing what the OP is proposing will do anything bad mechanically and it may just set the speedo at a more accurate speed. Currently they read high as it is.

+1
I'm looking around for one size larger now the RFT's are almost gone. On the rear i have 255, so one size larger is pretty exactly one more 1" in diameter. With M suspension it is lowered 20mm, so i would loose 12mm of the lowering. Yes affects speedo readings by 4% or so, but the thing is off by much more than that anyway on even brandnew tyres.
Someone in Germany did it with TUV approval - can't find the posting